The immunologic aspects of murine cytomegalovirus (MCMV) infections will be studied by establishing a model in C57B16 mice in which adult females will be immunized and their T cells, B cells, macrophages and immunoglobulins will be studied to determine which is capable of conferring protection on sucklings which are nursed by "immune" females. These factors will be inoculated into unimmunized lactating females to determine their fate and in particular whether they migrate from an intraperitoneal or an intravenous site to the breast and then via breast milk to sucklings. Sheep red blood cells will be similarly studied to provide a more readily defined marker.